Miscellaneous Shadow DOM

[josepharhar]

This was split from #181

Description

This is a bunch of WPTs in the shadow-dom directory that are failing. I don’t think they correspond to any particular big feature, they were just made from random one-off bugs.

Rationale

Basic Shadow DOM behavior should be interoperable.

Shadow DOM focus navigation, delegatesFocus, and element.focus()

Tests:
https://wpt.fyi/results/shadow-dom/focus-navigation
https://wpt.fyi/results/shadow-dom/focus
Spec:
https://html.spec.whatwg.org/C/#focus-processing-model
https://html.spec.whatwg.org/C/#sequential-focus-navigation

Shadow DOM events and retargeting

Tests:
https://wpt.fyi/results/shadow-dom/DocumentOrShadowRoot-prototype-elementFromPoint.html
https://wpt.fyi/results/shadow-dom/MouseEvent-prototype-offsetX-offsetY.html
https://wpt.fyi/results/shadow-dom/capturing-and-bubbling-event-listeners-across-shadow-trees.html
Spec:

• https://drafts.csswg.org/cssom-view-1/#dom-document-elementfrompoint
• MouseEvent is defined here but there is no definition for offsetX or offsetY: https://w3c.github.io/uievents/#idl-mouseevent
• capturing-and-bubbling-event-listeners-across-shadow-trees.html was discussed here: Composed and non bubbling event semantic dispatched in shadow tree whatwg/dom#742

[jgraham]

There appear to be open spec issues for these tests, and no clear path to consensus:
w3c/csswg-drafts#556 for elementFromPoint and web-platform-tests/wpt#15089 which affects the MouseEvent-offsetA-offsetY test.

Interop on shadow DOM beheviour is indeed very important, but to be included in Interop 2023 as a focus area, we really want a clear spec defining the tested behaviour. How likely is it that we can get consensus on the spec issues before the start of the Interop period?

[josepharhar]

If consensus is not reached in time, then I think we can just drop those two test files. There are plenty of other tests in the focus and focus-navigation directories.

[foolip]

In the MDN short survey on APIs & JavaScript, "Web Components (custom elements, Shadow DOM, etc.)" was the most popular choice by a fairly wide margin, selected by ~39% of survey takers.

Web Components was split into many granular proposals, and the survey results don't tell us which aspects web developers want the most, but it's fair to say that something about Web Components is important. (I'm posting this comment on each of the split proposals.)

[nairnandu]

Thank you for proposing Miscellaneous Shadow DOM for inclusion in Interop 2023.

We are pleased to let you know that this proposal was accepted as part of the Web Components focus area. You can follow the progress of this Focus Area on the Interop 2023 dashboard.

For an overview of our process, see the proposal selection summary. Thank you for contributing to Interop 2023!

Posted on behalf of the Interop team.